Here's Why Your Washing Machine Smells Like Sewage (and What You Can Do)

Have you opened your washing machine, expecting the fresh scent of clean laundry, only to be hit by a foul sewer odor? You're not alone. Many have experienced the perplexing issue of their washing machine giving off some seriously unpleasant smells. There are a few possible reasons your washing machine smells like sewage, and fortunately, there are also some fixes.

Washing Machine Plumbing Components

Before we explore the reasons behind the sewage-like smell in your washing machine, let's first understand the key plumbing components involved and their purposes in your laundry room.

Drain Pipe

The drain pipe is the flexible, usually gray colored hose that attaches your washing machine to your home’s plumbing. Its primary purpose is to carry wastewater away from the machine after the wash and rinse cycles and transfer the dirty water to your home’s sewage plumbing pipes.

P-Trap

This distinctive U-shaped plumbing component is installed beneath the stand pipe. The purpose of the P-Trap is to prevent sewer gases from entering the home. It does this by trapping a water seal, creating a water barrier that blocks sewer gases from escaping through the drain. 

Stand Pipe

A standpipe is a vertical pipe—usually a few feet tall—that connects the drain pipe to the home’s plumbing through the P-trap. This pipe provides a dedicated outlet for the washer's wastewater, preventing overflows, leaks, and backflow. Properly installed, the stand pipe ensures efficient water drainage during your laundry cycles.

Vent Pipe

A washing machine vent pipe is typically located behind the machine and extends vertically through the roof. This pipe allows air to enter the plumbing system, creating a smooth flow of wastewater drainage from the washer and preventing siphoning, traps, sewer odors, and blockages.

5 Reasons Your Washing Machine Smells Like Sewage

Now that we have a basic understanding of the plumbing components, let's explore the five main reasons why your washing machine might be giving off a sewage-like smell.

1. Problem With the P-Trap 

The P-Trap's water barrier can evaporate over time or be ineffective if the component isn’t installed correctly. When this happens, sewer gases can creep back into your laundry area.

2. Clogged Drain Pipe

A clogged drain pipe can lead to stagnant water in the washing machine's plumbing, which can develop a foul smell. This blockage may be caused by lint, debris, or soap scum accumulation.

According to data from Angi customers, 6% of people noticed a sewage smell as a result of clogged drains. A lot of homeowners (46%) also noticed that water doesn’t drain at all, so be on the lookout for a lack of drainage throughout your home if you notice strange smells around your washing machine.

3. Clogged Vent Pipe

Obstructions or clogs sometimes occur in the vent pipe. When this happens, it disrupts the proper flow of water and can result in sewage odors leaking back into your washer.

4. Too Much Detergent or Fabric Softener

Detergent can build up in your washing machine over time, and fabric softener is very hard on your system. When these two products sit in your washing machine or its drain pipes for a long time, they get difficult to break down. They also begin to harbor bacteria that can quickly cause a less-than-pleasant smell in your washing machine.

5. You Haven’t Run a Cleaning Cycle in a While

If you haven’t run a cleaning cycle in a few months, or if you don’t remember ever running one, that could explain the sewage smell. Cleaning cycles are important for, well, cleaning your washing machine and keeping foul smells at bay. Try to run a cleaning cycle once a month or every 30 washes, whichever comes first. 

What to Do When Your Washing Machine Smells Like Sewage

Now that we've identified the potential culprits, let's discuss what you can do to eliminate the unpleasant sewer odor from your washing machine.

1. Clean Your Washing Machine

Regularly cleaning your washing machine is essential and helps to eliminate odors, so make sure your appliance is completely clean. Wipe down any crevices and clean the rubber seal to prevent mold and bacteria buildup. Then, run a cycle with hot water, baking soda, and vinegar to eliminate debris and odors.

2. Correctly Identify the Source of the Smell 

Before taking any action, pinpoint whether the smell originates from the machine itself or the plumbing pipes. This will help you address the issue more effectively. To check if the smell is coming from the plumbing, disconnect the drain pipe and inspect it. If it's clogged or you smell a foul odor coming from it, clearing or replacing it may be necessary.

3. Pour Water Down the Drain Pipe 

For an effective P-Trap, water is needed. To rule out a P-Trap problem, pour water down the drain pipe. This replenishes the water barrier, preventing sewer gases from entering your home. If the smell disappears soon after, the problem was likely a dried out P-Trap.

4. Reach Out to the Pros 

If you still smell sewage after you’ve gone through all of these steps, there is likely a lingering plumbing problem or improper installation. It's best to contact a local sewer repair company to address clogged or improperly installed pipes since they can diagnose and resolve complex plumbing problems safely and efficiently.